5 Series [E39] (1997-2003)
The BMW E39 is the fourth generation of the BMW 5 Series range of executive cars, which was manufactured from 1995 to 2004.
These vehicles used either a BMW round pin or quadlock connector. As the factory switched between the 2 plugs at various stages, the easiest way to confirm which is to remove the factory radio. Some models will have the navigation system, which the stock radio is at the rear of the vehicle and is called a BM54.